BytecodeLens

The Java RE cockpit — decompile, attach, diff, patch.

A modern desktop reverse-engineering tool for Java / JVM bytecode. Four decompilers with automatic fallback, live JVM attach with hot-reload, industrial hex viewer with structure overlay, deobfuscation pipeline, headless CLI.

If this project helps you, please star it ⭐ — it helps others discover it.

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Why BytecodeLens

A desktop reverse-engineering workbench for the JVM. Not a decompiler UI — a cockpit that combines the best of JADX, Recaf, and JD-GUI, plus capabilities none of them have.

• Four decompilers with fallback that never fails. CFR · Vineflower · Procyon · ASM-skeleton. The Auto chain tries each with a 15-second timeout and falls through — you never see a blank tab.
• Live JVM attach + inspector. Attach to a running process by PID. Nine tabs of live data: heap/threads/CPU line charts, thread stack traces, deadlock detection, GC stats, per-pool memory breakdown. Hot-reload redefined classes into the target.
• Industrial hex viewer. Structure overlay that parses .class / ZIP / PNG into a clickable tree. Data inspector with 17 type interpretations (LE+BE). Find by hex/ASCII/UTF-16, go-to offset, copy as C-array, Shannon entropy graph, binary diff.

Features

Editor

• Decompiled / Bytecode / Hex / Compare tabs per class
• Compare tab with dynamic columns and per-column engine selector
• Edit decompiled source → javac recompile with phantom classes
• Assembler DSL for raw bytecode patching
• Hover highlight identifiers, Ctrl+click go-to-declaration, caret-line highlight
• Syntax themes: Primer Dark/Light, Dracula, Monokai, Solarized Dark/Light

Navigation & xref

• Expandable class tree (methods + fields inline, IntelliJ-style)
• Preview + pinnable tabs, drag-reorder, detach window
• Find Usages (Alt+F7 / X) with hierarchical tree, filter bar, code snippet preview under each call site
• Overriders / implementers appear in Find Usages results
• Recursive callers-of-callers tree with cycle detection
• Go to Class (Ctrl+N) fuzzy, Back / Forward navigation history
• Background decompile cache — package neighbours pre-warmed on a low-priority thread

Deobfuscation

11 transformation passes, plus two anti-tamper helpers:

• Dead Code Removal · Unreachable-After-Terminator (SC2-style) · Opaque Predicate Simplification
• Static Value Inlining · Call Result Inlining · Enum Name Restoration
• Illegal Name Mapping · Kotlin Name Restoration · Kotlin Data-Class Restoration
• Source Name Restoration · Stack Frame Removal
• Strip Code on field · Remove illegal annotations

Mapping

11 formats, both read and write:

• ProGuard/R8 · Tiny v1 · Tiny v2 · SRG · XSRG · TSRG · TSRG v2 · CSRG · JOBF · Enigma · Recaf
• Mapping diff / compose / invert for stacked refactor workflows
• Content-sniffing loader picks the right parser by file content, not extension

Search

• Modes: Strings · Names · Bytecode · Regex · Numbers · Comments (your own notes)
• String literal xref index built on load
• Streaming results with cancel + sort dropdown + progress
• Per-workspace package exclusion glob

JVM attach

• VirtualMachine.attach(pid) with dynamically-built agent jar
• Inspector opens instantly after attach — doesn't wait for a full class dump
• Live line charts refresh every 2 seconds (configurable)
• Hot-swap classes via Instrumentation.redefineClasses

Headless CLI

bytecodelens decompile app.jar -o out/ --engine auto
bytecodelens analyze app.jar --report-json report.json
bytecodelens mappings convert input.srg --to TINY_V2 -o output.tiny
bytecodelens mappings diff base.srg updated.srg --report-json diff.json

No JavaFX runtime loaded in CLI mode.

Customisation

• Full Settings window (Ctrl+,) with live-apply — 13 sections, ~50 toggles
• Customisable keybindings with IntelliJ / VSCode / Recaf / Default presets
• Per-workspace state: open tabs, divider positions, excluded packages, comments

Requirements

• Java 21 or newer (tested on JDK 25) — Adoptium Temurin recommended
• Windows 10+ / macOS 12+ / Linux (x64)

Install

Pick your platform on the latest release page:

Platform	Package	Notes
Windows	BytecodeLens-windows-x64.msi	Installer with Start Menu shortcut
macOS (Apple Silicon)	BytecodeLens-macos-aarch64.dmg	Drag to Applications
macOS (Intel)	BytecodeLens-macos-x64.dmg	Drag to Applications
Linux (Debian / Ubuntu)	BytecodeLens-linux-x64.deb	sudo dpkg -i BytecodeLens-linux-x64.deb
Any OS (portable)	BytecodeLens-1.0.0-all.jar	java -jar BytecodeLens-1.0.0-all.jar

Native installers bundle a JRE — no separate Java install needed. The portable jar requires Java 21+ on PATH.

Build from source

git clone https://github.com/Share-devn/bytecodelens.git
cd bytecodelens
./gradlew run         # launch the GUI
./gradlew shadowJar   # build bytecodelens-<version>-all.jar
./gradlew test        # 474 tests

CLI usage

The same jar doubles as a headless tool. The first positional argument decides the mode — recognised subcommands skip the JavaFX runtime entirely.

java -jar bytecodelens-1.0.0-all.jar help
java -jar bytecodelens-1.0.0-all.jar decompile app.jar -o out/
java -jar bytecodelens-1.0.0-all.jar analyze app.jar --report-json report.json

Contributing

Pull requests are welcome. See CONTRIBUTING.md for the build + style notes.

License

Apache License 2.0 — see LICENSE.

Credits

Built on top of excellent open-source projects:

• CFR · Vineflower · Procyon — decompilers
• ASM — bytecode library
• AtlantaFX — JavaFX theme
• RichTextFX — code editor widget
• Ikonli — iconography
• ControlsFX — extra JavaFX controls

Inspired by JADX, Recaf, and JD-GUI.

Comparison

	BytecodeLens	Recaf	JADX	JD-GUI
Four decompilers with fallback	✅	❌	❌ (single)	❌ (single)
Compare decompilers side-by-side	✅	❌	❌	❌
Edit + recompile Java	✅	✅	❌	❌
Live JVM attach + inspector	✅ (9 tabs)	✅ (6 tabs)	❌	❌
Hex viewer with structure overlay	✅	⚠️	⚠️	❌
Mapping formats	11	13+	13+	❌
Deobfuscation passes	11 + 2	23	Plugin	❌
Headless CLI	✅	✅	✅	❌
String decryption	✅ (BLPL + sim)	❌	Plugin	❌
JNI demangler	✅	❌	❌	❌
Android (APK / DEX)	❌	✅	✅	❌
License	Apache 2.0	MIT	Apache 2.0	GPL-3.0

Keywords

Java decompiler · JVM bytecode editor · bytecode viewer · reverse engineering · deobfuscation · JVM reverse engineering · Java bytecode analysis · jar analyzer · class file viewer · CFR decompiler · Vineflower · Procyon · ASM · hex editor · JVM attach · JavaFX bytecode tool · static analysis · obfuscator detection · Kotlin decompiler · Java hot reload · mapping converter · SRG · TSRG · Tiny · Enigma · Recaf alternative · JADX alternative · JD-GUI alternative